Helicoptors in this sort of setting, I would imagine, would be best-used by early nations that might not have VTOL-friendly technology/atmosphere 3D-operating craft. I can imagine most of them get their blades replaced with VTOL engines, though, since they could gain more engine power utilizing future-tech to more or less match the efficiency of a bladed-chopper.
I guess it might be a good subject, though, to find out how viable heliflopters are still in comparison to these crafts and if Nepleslia even fields them. I'll do some digging on the Nepleslia front.